正值青春期的少女艾玛(苏菲·瓦瓦希尔 Sophie Vavasseur 饰)因小事与父母发生争吵,继而用玻璃碎片割破自己的手掌。在此之后,父母子女的关系虽有所松动,但是新的危机已悄悄展开。艾玛是不是会做出些奇怪的举止,这令父母异常担心,于是只得将艾玛留在家中接受教育。期间他们尝试带女儿去看具有催眠本领的心理医生,谁知医生最终猝死艾玛的膝上。艾玛自感自己已被魔鬼附体,因此不顾崇尚科学的父母的反对,执意求助于因驱魔失败而被革除神职的舅舅基斯(道·布莱德利 Doug Bradley 饰)。 基斯似乎渐渐证实了艾玛的猜测,而她体内那股邪恶的力量也变得越来越强大……Fifteen year-old Emma Evans has an argument with her mother Lucy since she wants to go to a concert in London with her friends Rose and Alex. Emma immediately has a convulsion and her family takes her to the hospital, but the doctors do not find any physical problem. Then her father John tries to convince his wife to send Emma to school, instead of homeschooling, but she prefers to keep Emma in the family-based education. Lucy sends her daughter to the psychoanalyst believing that she has psychological problems and Emma asks her friend Rose to record her session of hypnosis though the cellular but the doctor dies during the session. When Emma listens to the tape, she believes she is possessed by the devil and asks her parents to be submitted to an exorcism with her uncle, Priest Christopher Taylor. However her skeptical mother is against the ritual and recalls that Chris was responsible for the death of a teenager, Ana, in the past in an unsuccessful exorcism. But when Emma levitates in the kitchen in front of her family, her parents call Chris.